The present disclosure relates to memory systems and, more particularly, to a memory module including an on-die termination circuit and an on-die termination control method thereof.
A data signal transmitted along a transmission line of a memory system may be reflected at the termination end of the transmission line. The reflected data signal acts as a noise to have an influence on an original data signal and degrade the quality of the data signal. A termination resistor is connected to the terminal of the transmission line to prevent reflection of the data signal.
The termination resistor is a component used to reduce reflection of the data signal and to prevent lowering of quality of the data signal by matching between internal impedance and external impedance of a memory system. The termination resistor is typically used for a dynamic random access memory (DRAM) having high operating speed. Recently, to prevent signal interference between DRAMs, an ODT (On Die Termination) technique is typically used for connecting the termination resistor to the interior of the DRAM.
Since a DRAM has very high operating speed higher than 1000 MHz under DDR3 SDRAM (Double Data Rate 3 Synchronous DRAM) standards, higher quality and stability of the data signal are needed. If impedance is not matched due to variation in a value of the termination resistor depending on variation in a fabrication process, a power supply voltage, and an operation temperature, it is difficult to transmit a data signal at high speed. Thus, the data signal can be distorted.
A plurality of DRAMs included in a memory module may have different signal transmission characteristics according to their mounted positions, respectively. Accordingly, when these environmental factors are precisely compensated, accurate impedance matching may be possible in the memory system.